WASHINGTON — One of the federal government’s main efforts to push Americans to prepare for climate threats is in question after the Senate majority leader’s office objected to a plan to adjust flood insurance rates.

The Federal Emergency Management Agency was preparing to announce new rates for federal flood insurance on April 1, so that the prices people pay would more accurately reflect the risks they face. The change would very likely help reduce Americans’ vulnerability to floods and hurricanes by discouraging construction in high-risk areas. But it would also increase insurance costs for some households, making it a tough sell politically.